WASHINGTON — After studying traffic jams for two years, a National Research Council panel has decided that the best way to curb highway backups is to impose fees on commuters who drive at peak hours.

"In response to these fees, some motorists would vary the times they travel, alter their routes, car-pool, use public transit, choose other destinations or avoid some trips," the panel said in a report released Tuesday. The National Research Council is an arm of the National Academy of Sciences. The study was financed by the Federal Highway Administration.

Many companies, from long-distance phone carriers to airlines to restaurants, charge more for their services during high-traffic periods. And a renewed emphasis on efficient transportation, coupled with motorists' rising frustration with delays, is fueling interest in "congestion pricing" on busy highways across the nation, including Southern California.

Peak-period fees averaging 10 cents to 15 cents a mile, or $2 to $3 for a daily round trip, would reduce congestion by 10% to 15% and cut commuting time by about 20%, the panel estimated. Off-peak tolls would vary depending on traffic conditions. Reducing highway traffic would also cut down on ozone-depleting emissions and fuel consumption, the report said.

Current technology would allow the fees to be collected electronically, the report said. Computers in toll booths could communicate with electronic tags on motorists' dashboards, allowing commuters to prepay the fees or have their accounts debited without stopping.

"It has become clear that America's metropolitan areas cannot build their way out of congestion," said Martin Wachs, chairman of the National Research Council committee and a professor of urban planning at UCLA.

Federal support for the idea so far has been limited, but the Transportation Department is funding a handful of pilot programs for congestion-pricing around the country.

The panel urged Congress to increase funding for the programs in 1997, when the Intermodal Surface Transportation Efficiency Act, which includes money for the experiments, will be reconsidered. One proposed government experiment would hike the $1 toll on the San Francisco Bay Bridge by $1 or $2 during peak hours.

But congestion-pricing proponents acknowledged that winning wider support for the concept, both on Capitol Hill and among motorists, will not be as easy as taking a Sunday drive.

"Public and political perceptions about fairness and about motorist resistance to paying for services which they previously viewed as free will be significant obstacles," Wachs said.

Although the Transportation Department set aside $150 million in its budget to support congestion-pricing experiments last year, only 16 transit authorities submitted plans for the projects. Part of the reason for the tepid response, transportation officials said, is that lawmakers are leery of backing a program that could be interpreted as a road-use tax.

The best way to market rush-hour tolls to drivers, a Federal Highway Administration expert said, would be to use the new toll revenue for public transit or to offset local gas taxes.

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Motorists' groups derided the idea, saying that "a tax by any other name is still a tax," and they argued that commuters should not have to pay to use a road that they already had financed with tax dollars.

"Peak-period pricing's effectiveness stops where theory and reality meet," said Lester P. Lamm, president of the Highway Users Federation. "While the report outlines a variety of theoretical ways to compensate for peak-period pricing's massive inequities, it ignores the political reality of current tax needs."

The American Automobile Assn. called congestion-pricing unnecessary. AAA data shows that the nation's highways took on 22 million new commuters between 1980 and 1990, while the average commuting time increased by only 42 seconds to about 23 minutes.